Hidden Coherence Bursts and Time-Tagged Holevo Fragment Information Under Finite-Resolution Observation in a Central-Spin Environment.

We study a structured QND central-spin testbed under a hybrid finite-resolution protocol. The central-spin state is temporally integrated without retaining the internal readout-time label, whereas environmental fragment information is quantified by a time-tagged scalar-averaged Holevo benchmark. On a converged numerical grid, we identify finite time regions in which the integrated central-spin state has low off-pointer visibility while model-resolved late-time coherence bursts remain present and the typical-fragment Holevo benchmark exceeds a prescribed threshold. A detector-window variance decomposition supplies a model-assisted diagnostic; it requires a fine-grained trajectory or a microscopic model. The Holevo quantity is an upper bound on accessible classical information, and no fragment measurement attaining it is constructed. Grid refinement, an independent trapezoidal quadrature, and a half-cell grid shift preserve the qualitative four-region baseline structure. A sampled-subset calculation benchmarks the typical-fragment classification, but we do not establish constructively disjoint or state-integrated fragment redundancy. A single-realization detector-width/disorder map and a 100-realization ensemble delimit the structured mesoscopic scope. The dimensional conversion is an NV-like scale estimate for an engineered quasi-homogeneous testbed and not an experimental protocol for an arbitrary natural bath.